The invention concerns integrated circuit devices designed to be incorporated into portable memory objects and, in particular, into portable memory objects in the card format.
Smart cards are generally used in applications in which the security of the storage and processing of confidential information is essential. These cards are designed particularly for applications in the health care field, pay television applications, or so-called electronic purse applications.
They are composed of a plastic card body into which an integrated circuit is incorporated. This can be an electronic module comprising an integrated circuit chip, or the integrated circuit chip itself.
The amplitude of the current Idd consumed by an integrated circuit is time dependent. The amplitude of the current Idd during which the integrated circuit performs a task for a certain period of time constitutes a current signature of the task. The analysis of this electric signature, and more precisely of its shape, reveals the activity of the device and makes it possible to access confidential information contained in said device.
In order to prevent such a signature analysis, certain methods of the prior art, in a first example, propose to use programming algorithms that in particular cause the triggering of operations at pseudo-random moments, or in a second example, propose to generate noise that is rich in random information or in erroneous operations.
These methods of the prior art have many disadvantages. They monopolize certain resources of the device, resources which could be used for performing other operations, and they are not resistant to detailed signature analysis.
One object of the invention is to protect access to confidential data by making the analysis of the electric signatures of integrated circuit devices more complex.
This and other objects are attained in accordance with one aspect of the invention directed to an integrated circuit device designed to be incorporated into a portable memory object, particularly in the card format, characterized in that it comprises at least one capacitor capable of attenuating the amplitude of the peaks of the current consumed by the integrated circuit of said device.
Advantageously, the capacitance has a value greater than about 0.1 nanofarad, particularly on the order of 1 nanofarad; the device also comprises at least one electrical resistor; the electrical resistance is characterized by a value greater than about 1 ohm, particularly on the order of 10 ohms; the resistor is a self-inductor; the self-inductance is characterized by a value greater than about 50 nanohenries, particularly 500 nanohenries; the capacitor is electrically connected both to a first pad or first region of the integrated circuit device and to a second pad or second region of the integrated circuit device, the first and second pads or the first and second regions being capable of being passed through by a supply current of the integrated circuit; the first pad is the contact pad Vss or the first region is the contact region Vss and the second pad is the contact pad Vdd or the second region is the contact region Vdd; the self-inductor is electrically connected to the second pad or to the second region of the integrated circuit device and connected in series with the capacitor; the capacitor is integrated into a supplementary layer of a chip; sub-layers forming electrodes of the capacitor are electrically connected to pads of the integrated circuit device; the self-inductor is in the form of a coil, integrated into an active side of a base layer of the integrated circuit device.